How does Marlene Reed Wetzel use imagery in A Map of Tripoli, 1967?

In Section Two, Wetzel uses a metaphor to describe Lucia in her newly pregnant condition as, "She was scarcely pregnant, just enough to look ripe, and her hair was tied back with a ribbon. The dress was purple, the color of eggplants--the egg was planted!" The imagery is perfectly crafted to represent the slightly swollen woman dressed in purple, mimicking the shape of the glossy, purple vegetable.